koa-jsonwebtoken

koa-jsonwebtoken

Koa middleware to validate/revoke/refresh JSON Web Tokens. Sets ctx.state.user(default) to token payload.

Install

$ npm install koa-jsonwebtoken

Retrieving the token

The token extraction strategy needs to be specified explicitly by setting opts.extractToken. The module provides two strategies namely fromAuthorizationHeader and fromCookies. The token is normally provided in a HTTP header (Authorization), but it can also be provided in a cookie by setting the opts.cookie option to the name of the cookie that contains the token. Custom token retrieval function should match the following interface:

/**
 * Your custom token resolver
 * @param  {object}       ctx object passed to the middleware
 * @param  {object}       middleware's options
 * @return {String|null}  resolved token or null if not found
 */

Passing the secret

A single shared secret needs to be specified explicitly in opts.secret.

Check for revocation

In case you maintain a blacklist for the purpose of token revokation, you can specify a custom function to check for revocation by setting opts.checkRevoked. The function should match the following interface:

/**
 * Your custom token revocation check function
 * @param  {object}       decoded token
 * @param  {object}       middleware's options
 * @return {Promise}      Promise resolves with anything or rejects with {message: "reason"}
 */

Refresh token

To refresh your tokens in case they are expired and do so in a manner transparent to the user, you can set opts.refreshCookie to the name of the cookie where the server will expect the refresh token. You also need to specify opts.doRefresh with a custom function which will carry out the refresh logic/validate the refresh token. The function should match the following interface:

/**
 * Your custom token refresh function
 * @param  {object}       ctx object passed to the middleware
 * @param  {object}       middleware's options
 * @param  {string}       refresh token from the specified cookie
 * @param  {object}       decoded access token
 * @return {Promise}      Promise resolves with anything or rejects with {message: "reason"}
 */

Note: ctx.state[opts.key] is set to the stale payload after your custom function returns. Don't modify critical payload fields if you depend on them in your application.

Example

import koa from 'koa';
import jwt, { fromAuthorizationHeader } from 'koa-jsonwebtoken';
// const jwt = require('koa-jsonwebtoken').default;
// const fromAuthorizationHeader = require('koa-jsonwebtoken').fromAuthorizationHeader;
const app = koa();

// Custom 401 handling if you don't want to expose koa-jsonwebtoken errors to users
app.use(async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    if (401 == err.status) {
      ctx.throw(401, 'Protected resource, use Authorization header to get access\n');
    } else {
      ctx.throw(500, err.message);
    }
  }
});

// Unprotected middleware
app.use(async (ctx, next) => {
  if (ctx.url.match(/^\/public/)) {
    ctx.body = 'unprotected\n';
  } else {
    await next();
  }
});

// Middleware below this line is only reached if JWT token is valid
app.use(jwt({ secret: 'shared-secret', extractToken: fromAuthorizationHeader }));

// Protected middleware
app.use((ctx) => {
  if (ctx.url.match(/^\/api/)) {
    ctx.body = 'protected\n';
  }
});

app.listen(3000);

Alternatively you can conditionally run the jwt middleware under certain conditions:

import koa from 'koa';
import jwt, { fromAuthorizationHeader } from 'koa-jsonwebtoken';
const app = koa();

// Middleware below this line is only reached if JWT token is valid
// unless the URL starts with '/public'
app.use(jwt({ secret: 'shared-secret', extractToken: fromAuthorizationHeader }).unless({ path: [/^\/public/] }));

// Unprotected middleware
app.use(async (ctx, next) => {
  if (ctx.url.match(/^\/public/)) {
    ctx.body = 'unprotected\n';
  } else {
    await next();
  }
});

// Protected middleware
app.use((ctx) => {
  if (ctx.url.match(/^\/api/)) {
    ctx.body = 'protected\n';
  }
});

app.listen(3000);

For more information on unless exceptions, check koa-unless.

If you prefer to use another ctx key for the decoded data, just pass in key, like so:

app.use(jwt({ secret: 'shared-secret',
              extractToken: fromAuthorizationHeader,
              key: 'jwtdata' }));

This makes the decoded data available as ctx.state.jwtdata.

You can specify options to control the verification as well. See node-jsonwebtoken for more options:

app.use(jwt({ secret:   'shared-secret',
              audience: 'http://myapi/protected',
              issuer:   'http://issuer' }));

If the JWT has an expiration (exp), it will be checked.

This module also support tokens signed with public/private key pairs. Instead of a secret, you can specify a Buffer with the public key:

var publicKey = fs.readFileSync('/path/to/public.pub');
app.use(jwt({ secret: publicKey }));

Related Modules

• jsonwebtoken — JSON Web Token signing and verification

Note that koa-jsonwebtoken exports the sign, verify and decode functions from the above module as a convenience.

Test Server

$ npm install
$ npm run test

Author

Sid Jain

Credits

This code is largely based on: koa-jwt (unmaintained).

License

The MIT License